Process and apparatus for making piston rings



June 10, 1930. L. c. MARSHALL 1,762,556

PROCESS AND APPARATUS FOR MAKING PISTON RINGS Filed June 1, 1927 3 Sheets-Sheet 1 v karma:

June 10,1930. c. MARSHALL PROCESS AND APPARATUS FOR MAKING PISTON RINGS Filed June 1, 192'? 3 Sheets-Sheet 2 Iii .J

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{WW Maw! June 10, 19%.. L. c. MARSHALL PROCESS AND APPARATUS FOR MAKING PISTON RINGS 3 Sheets-Sheet 3 Filed June 1, 1927 Patented June 10, 1930 PATENT OFFIC LEWIS C. MARSHALL, OF WALPOLE, MASSACHUSETTS PROCESS AND APPARATUS FOR MAKING PISTON RINGS Application filed June 1, 1927. Serial No. 195,719.

This invention relates to an improved method of and apparatus or machine for continuously manufacturing resilient piston rings from an elongate strip of wire. In my copending application, 1 Serial No. 62,825, filed October 16, 1925, I have disclosed a process of making piston rings from high carbon steel wire or rod, that is to say steel of at least 0.5% carbon, or an equivalent alloy and onev of the steps of said process consists in bending the wire to form a rough or embryo ring. In said pending application I stated that this initial bendin of the wire might be performed in any sultable manner 1 and by means of appropriate apparatus, and

the present invention relates more specifically to a novel and advantageous method of bending the wire or rod which is particularly appropriate to the production of piston rings in accordance with my aforesaid general process, (as described in my abovenoted co-pending application) and to improved apparatus for use in the practice of the present method.

In accordance with the present invention I progressively bend a length of wire or rod of suitable cross section, e. g. rectangular or keystone shape, to form a coil or helical turn, each turn if desired being distorted from true circular form, and 1 successively cut 011' ortions from the helix, each such portion a'ving a circumferential length slightly less than that of one complete turn of the helix. Preferably the pitch of the helix is so graduated, in relation to .the modulus of elasticity of the wire that, as soon as a turn is cut off, it will assume the shape of a substantially flat coil. The rough rings made by this method may now be subjected-to appropriate finish- 40 ing operations, such for example as those described in my aforesaid pending application, or modification thereof, in order to provide them with the desired dimensions necessary to permit them accurately to fit within the groove of a piston and to provide a as tight seal between the same and the c lin er wall.

The apparatus herein descri ed is illustrative o appropriate means for performing the bending process just described and is adapted to permit rapid and automatic prothe wire bending an duction of the rough piston rings. The apparatus illustrated consists of a wire coiling machine of conventional form, having certain of its elements rearranged, and certain elements added thereto to permit the eflicient production of piston rings. For example, if the ring is to be non-circular as initially formed, which is sometimes desirable, the usual wire coiling arbor may be provided with a flattened surface.- Cooperating with this flattened portion of the arbor is an intermittently movable coiling point which is adapted to distort the wire as it advances to prevent it from following an exactly circular or helical path, or, in other words, to provide the coil with a varying radius of curvature,

so that when the finished ring is located within a cylinder and compressed, it will exert a substantially uniform pressure throughout the circumference of the cylinder, thus pro- 7 viding a gas tight joint. A pitch cam with a tapered surface is located adjacent to the path of the wire for guiding the wire along a helical path of such a gradual pitch that the wire will not be stressed beyond its'limit of elasticity, so that as soon as a shaped turn is cut from the helix, it will assume substantially the form of a flat coil rather than that of a portion of a helix An intermittently movable member is adaptedto hold the wire against a ortion of the arbor at the instant that the s caring member starts cutting the same in order to prevent the cutting operation from causing an appreciable lip or extrusion upon the severed wire ends.

.The above and further advantageous features and objects of the invention will'be all)- parent to those skilled in the art upon a rea ing of the subjoined description and claims in conjunction with the accompanying drawin s, in which ig. 1 is a side elevational view illustrating a preferred embodiment of apparatus usefu in the practice of my novel method;

Fi 2 is an elevational view of a portion 96 of t e opposite side of the apparatus of Fig. 1; v

ig. 3 is an enlar ed elevational detail of 5 cutting mechanism; Figs. 4 and 5 are similar views of a por- 100 tion of that mechanism, showing the parts in than that shown in Figs. 3,4 and is directed.

Fig. 10 is a side elevational view of the arbor shown in Figs. 3, 4 and 5;

Fig. 11 is a combined side, end, and bottom view of the form of arbor shown in Fig. 9;

Figs. 12, 13'and 14 are detail views showing dlfierent typesof gaps which may be provided in a piston ring made in accordance with the resent invention; and

Fig. 15 is an enlar ed transverse section of a preferred form 0 wire useful in making rings by this method.

Themachine disclosed herein has an upstanding frame or plate 1 which supports the various component elements, driving gears, etc., for bending a length of wire or rod toform successive pistonrings and to sever the latter from the wire. For this purpose the machine is provided with a series of feed rolls 2 which are grooved as designated by-numeral 3 to receive andgrip the wire or rod. Suitable adjusting mechanism 4 is adapted to control the relative positions of pairs of feed wheels 2 in a manner which is well known in the wire coiling art. Between and adjoining feed wheels 2 are guide plates 6 which are provided with grooves 7 in order to guide the wire accurately to the wire bending mechanism. The wirebendin mechanism includes an arbor 10 toward w ich the end of the wire This arbor 10 may con- Veniently be located u on a support 12 which is held to the frame 1' y key 70 (Fig. 9). If the rings are to be formed initiall of noncircular shape, the arbor 10 is provlded with a surface 11 in the form of a compound curve,the. wire during the major portion of its'movement being adapted to bearonly upon the end portions of this surface but being intermittently forced against the flattened portion of the surface 11 to cause the wire to follow a curved path of varying radius and thus to make each coil of'a distorted or flattened helical form. For this purpose I provide a coiling point preferably in the form of a grooved roller 16, which normallybears against the curved wire opposite to the flattened intermediate portion of sur-.

face 11, Fig. 3, in ordeito impart the de-' sired curvature to the moving wire.

While I may use wire of any desired cross section, I prefer to "employ wire at of the keystone section shown in Fig. 15. When such wire is bent with the narrow face n at the inside of the bend, the flow of themetal under the bending stress tends to restore the wire horizontally disposed guideways 170, Fig. 3,

and has an outstandin boss 71 upon which the arm 17 is clampe by clamp screw 72, while the lateral position of aim 17 in relation to plate 1 may be adjustably fixed by screw 73, Fig. 7. Thus the grooved roller 16 may be properly located in relation to the path of the wire. Before the end of a new wire strip is fed through the machine by hand, clamp screw 72 may be loosened and arm 17 swung upwardly. An adjustable stop 19 is adapted to engage the lower surface of arm 17 in order toaid in repositioning the arm 17 following this opposition.

Properly synchronized with the wire feeding mechanism, I provide the rotatable cam 20 which is mounted upon the shaft 21 and adapted intermittently to bear against a roller 22 carried by a follower lever 23, Fig. 2. Thecam 20 preferably comprises a pair of separate cam plates 63 which are disposed between two disks 64 keyed to the shaft 21. The parts 63 and 64 are preferably provided with segmental slots 65 adapted to permit the clamping of the cam plates 63 in the desiredrelation to each other. Thus the effective circumferential extent of the rise of the cam 20 may be determined by the relativeposition of the plates 63 in order adjustably to vary the effective length of the period during which follower 23 is depressed. This follower, when thus acted upon by the cam, is adapted to swing a lever 24 downwardl against the tension of a spring 25 and to osci late a bell crank 26 through an adjustable link 27. The other end of the bell crank 26 has a ball and socket engagement with the slidable carrier 69 upon which the-arm 17 is mounted. Thus cam 20, bearing upon roller 22, will cause the member 16 to press the wire firmly against theflattened midportion of arbor surface 11, intermittently caus-' ing a variation in radius of curvature of the wire.

A suitable guide member or pitch cam 30 is adjustably mounted upon the support 12 which also holds arbor 10 and the adjoining guide plate 6. Guide member 30 is provided with a apered 30 which normally lies in the arranged upon a" bolt 76 that holds the pitc cam 30 to the sleeve. A clamp 77 holds the sleeve 7 5 in properly adjusted position radially while a set screw 78 is adjustably mounted upon clamp 77 by nuts 79 and is screwed into the member 12 in 4 order to determine the transverse position of pitch cam 30.

When the wire has been bent to form a helical turn, the cutting means operates to.

cut off a segment-a1 portion of the wire. Preferably the severed turn has a circumferential length somewhat less than that of a circle of corresponding size. In other words, aTcircumferential gap is left in the severed turn such as is conventional in the manufacture of piston rings. Mechanism for this purpose is shown in its various operative positions in Figs. 4 and 5. This mechanism comprises the acute edge 33 of the'arbor 10 and the cooperating shearing member or cutter 34. Cutter 34 has a cutting edge 35,- adjoining which its surface is provided with-a curved recess 36 substantially corresponding to the normal curvature of the bent wire at the instant it engages the same to -start cutting thereof. The shearing mechanism may be operated in any conventional manner; for example, as illustrated in Fig. 1, the driving shaft 21 is provided with the cam 41 (shown in dotted lines) which engagesa roller 43 carried by a member 44 mounted'upon a shaft 45. The shaft 45 carriesa crank 47 to which the cutter 34 is secured by a clamp 48. At the end of crank 47 is the cam surface 49 which is adapted to engage a rocker 50, (Figs. 4and 5) pivotally supported by the frame. Upon the opposite end of the rocker is mounted the finger 5l'which is provided with a curved end surface to conform to the shape of the wire coil and which is moved into-engagement with the same at a pointclosely adjoining the path of the cutting edge 35. Thus the wire from which the ring portion is to be severed is held between the finger 51 and the surface 11 of arbor 10 to permit accurate shearing of the wire and to avoid appreciable flowing of the metal due to the shearing operation, it being understood that forward longitudinal movement of the wire ceases during the cutting operation. Spring 62 normally retracts finger 51 from its position in engagement with the wire so that the finger 51 only presses the wire against arbor 10 when the shearing member 34 is being operated by crank 47 to sever the wire...

Fig. 9 shows a form of mechanism which is generally similar to that described above with the exception that the cutting edge upon arbor 110 is beveled as indicated at 67, Figs.

providing stepped joint of the configuration shown in Fig. 14.

A machine of the character disclosed herein may be used automatically to make piston rings from a strip of wire of suitable cross section, for example, rectangular, though preferably of thekeystone section shown in Fig. 15. This process can be carried on at a very low cost and is adapted to permit the manufacture of a very large number of rings within a short interval of time. The process permits manufacture of rings from hard steel wire having a comparatively high carbon content, for example, more than 0.5% of carbon or alloy steel having equivalent physical characteristics. In carrying out the process, wire is first introduced manually between the rolls 2 and guide elements 6 and the end thereof is bent about arbor 10 under roller 16. Thereupon the driving mechanism of the machine may be started automatically to perform the successive operations to make the piston rings, the wire being bent about the arbor and preferably intermittently flattened so that each coil is given a distorted circular form, as shown in Fig. 6, in order to provide a ring which expands uniformly when located within the engine cylinder. As the wire continues-to move it is guided into a helical path, the pitch of which is so moderate that the limit of elasticity of the wire is not exceeded. The advance of the wire is then momentarily stopped due to the synchronized relation of the cutting and feeding mechanisms, as is common with wire coiling machines, whereupon the wire is cut off by the action of the shearing member 34 or 134; the cutting operation, being aided and made more accurate due to the action of the retaining finger 51 in firmly holding the unsevered portion of wire 1 at a point adjoining the cut therein. Preferably the cutting mechanism is so timed in relation to the feeding mechanism that each severed turn of wire comprises slightly less than a complete circle. Thus, as each ring is severed from the wire, it drops from the machine substantially in the form of a plane or flat coil having a varying radius and a small gap therein, or, in other words, each severed turn constitutes a rough piston ring ready for such final finishing operations as may be necessary to bring it within the close tolerances demanded by automotive practice.

Under some circumstances, as when for cxmaple the'after treatment of the ring is of suitable character, it may be unnecessary to vary the radius of. curvature of the wire during bending, and in that event the cam 20 may be removed, so that each turn of wire as severed will be of substantially circular contour. I

It is thus evident that the machine and process disclosed and described herein may be utilized for converting a continuous strip of wire of appropriate cross section into piston rings which require only final grinding or said wire endwise while bending its end portion to form a turn, and cutting off each said turn at such a point as to provide a substantially plane ring having a'gap therein.

2. That method of making tough and resilient piston rings of a character such that will not score the wall of a cylinder which comprises as steps bending the end they ' portion of a length of steel wire of at last 0.5 per cent carbon content to form a helical turn and cutting off each said turn from the length of wire at such a point as to provide .a substantially plane ring having a gap therein.

which comprises advancing a length of steel wire of approximately 0.65 per cent carbon content, bending the forward end portion of said wire while constraining said end portion to move in'a helical path of a pitch such that the wire. acquires substantially no helical set thereby forming a helical turn, cutting off said turn from the length of wire, and releas- I ing said turn to permit it to assume the form of a substantially plane ring.

i curvature of varying radius, and cutting off 4 That method of making piston ringswhich comprises as steps selecting steel wire of atleast 0.5 per cerijtscarbon content, progressively advancing-gthe end portion of the wire while constraining it to move in a helical path of such pitch that the wire acquires substantially no helical set thereby forming a helical turn having a resilient tendency to assume the form of a plane ring, and cutting off said turn from the wire at such a point as to provide a ring having a gap therein.

5 The method of making piston rings from an'elongate strip of wire which comprises as steps bending the end of a portion of the wire to form a helical turn having a.

the resulting turn of wire to provide a ring with a slight gap therein.

6. That method of making piston rings from an elongate strip of wire which comprises as steps bending the end of the wire by moving it through ahelical path of varying radius and cutting of? the resulting turn of wire to provide a ring with a slight gap therein.

' pitch of said helix being within the elastic limit of the wire, and cutting ofi the resulting turn of wire to provide a ring with a slight gap therein. I I

8. The method of making piston rings from an elongate strip of wire which comprises as steps progressively directing the end portion of the wire along a curved path, applying pressure to the wire to vary the radius of curvature of the path, whereby a helix is formed, cutting a ring with a gap thereln from the end of said helix, the pitch of the helix being within the elastic limit of the wire whereb the ring will spring into the form of a su stantially flat coil.

, 9. The method of making piston rings from an elongate strip of wire, which comprises as steps progressively bending the end portion thereo. into a helix having a pitch of an order which does not permanently distort the wire turns materially from the shape of a flat coil, and cutting from the wire helix successive helical'portions which have circumferential dimensions slightly less than 3. That method of making piston rings that of one coil of the helix, whereby substantially flat rings with circumferential gaps are provided. I,

. 10. The method of making piston rings from an elongate strip of wire, which comprises as steps progressively bending the end portion of the wire into a helix, each windmg of-which is slightly flattened to provide it with a circumferentially distorted form and which has a pitch of an order which does not permanently distort the wire turns materially from the shape of a flat coil, and cutting ofi' wire turns from the helix. 11. That method of making plston rmgs from steel wire of at least 0.5% carbon which comprises as steps advancing a length of wire while causing it to pass between forming tools whereby to lmpart an arcuate curvature to the advancing end, and severing the wire by a single diagonal out at such a point as to form a substantially plane ring having a gap therein.

12. That method of making piston rings from hard steel wire which comprises as steps advancing a length of wire while causing it -to pass between bending tools which impart an arcuate curvature thereto, and severing the wire by a single out before said length has formed a complete circle, thereby producing a ring having a gap therein, the out being diagonal to the plane of the ring.

13. That method of making piston rings from hard steel wire which comprises ad.- vancing a length of wire between bending tools to impart an arcuate curvature of intermittently varying radius to the wire, intermitting the advance of the wire, severing the bent wire at a point such as to form a ring having a gap therein,'and again advancing the wire. 1

14. That method of making piston rings from hard steel wire which comprises intermittently advancing a length of the'wire between bending tools which constrain the end of the wire to move in a helical path of intermittently changing radius of curvature, and

severing the bent wire in the interval beit between normally fixed bending devices which constrain the advancing wire to assume an arcuate curvature, and varying the relative position of the bending devices during the advance of the wire whereby to vary the radius of curvature of the wire.

16. That method of making piston rings from hard steel wire which comprises as steps advancing alength of wire while confining it between normally stationary bending devices which constrain the advancing wire to assume an arcuate curvature, intermittently changing the relative position of the bending devices whereby to vary the radius of curvature of the wire, and after a predetermined number of such changes in relative position of the bending devices, severing the wire to form a single ring-like turn.

17. That method of making piston rings from hard steel wire which comprises as steps advancing a length of wire while confining it between relatively movable bending devices which constrain the wire to assume an arcuate curvature, varying the arcuate position of said bendlng devices first to increase and subsequently to decrease the ''radius of curvature of the wire duringthe formation of a single ring-like turn of the wire, and severing such ring-like turnfi 1 18. Thatmethodofrmaking piston rings a from hard steel wire which comprises as steps and means for bending the advancing wire to form a substantially helical coil while imparting an arcuate curvature of intermittently varying radius to each winding of the coil.

20. A machine of the class described, comprising means or bending wire into a substantially helical coil and for automatically flattening each winding of the coil, said means comprising a fixed arbor and a member intermittently movable to press the wire into firm engagement with the arbor.

21. A. machine of-the class described, comprising means for bending wire into a substantially helical coil, and means for automatically varying the radius of each winding oflthe coil, said means comprising a fixed arbor and a coiling point, the former having a curved surface defining the path of the wire and adapted to hold the wire against the coiling point, the latter being intermittently movable to press the wire into firm engagement with the curved surface arbor.

22. A machine of the class described, comprising wire feeding mechanism, means for bending wire into a substantially helical coil, and means for automatically varying the radius of each wi ndin of the coil, said means comprising a fixed ar r and a coiling point intermittently movable to press the wire into 'firm engagement with the arbor, said coiling point being controlled by a cam connected to the wire feeding mechanism.

23. A machine ofthe class described, comprising means for bending wire into a substantially helical coil, and means for automatically flattening each winding of the coil, said means comprising a fixed arbor and a roller intermittently movable to press the wire into firm engagement with the arbor, said roller being mounted upon the end of a movable member, and a cam adapted intermittently to move the roller toward the arbor.

24. A machine of the class described comprising means for bending wire into substantially helical form, intermittently movable means for cutting portions from the helix thus formed, and means synchronized therewith and designed to grip the wire adjoining the cutting point at the instant of cutting.

'25. .A machine of the class described comprising means for progressively bending the end of a strip of wire into helical form, means for cutting off successive portions of the helix, said means comprising relatively movable shearing members and means synchronized with the same to hold the wire against one of said shearing means at the instant of cutting.

26. A machine of the class described, comprising means for bending wire into a substantially helical coil, and means for automatically varying the radius of each winding of the coil, said means comprising members defining the path of the helically bent wire, means normally holding these members in spaced relation to each other and means intermittently forcing them toward each other firmly to engage the moving wire.

27 A machine of the class described, comprising means for bending the end of a continuously moving strip of wire into the form of a segment of a circle, means for successively cutting bent portions from the end of the wire, and a tapered member in the path of the advancing wire end adapted to engage successively presented ends of the wire from which a portion has thus been severed and to guide each such end along a helical path.

28. A machine of the class described, comion prising wire coiling means, and means for 7 cutting turns off the coiled wire, said cutting means comprising relatively moving cutting elements, and wire gripping means whereby the wire at one sided the line of severance may be gripped during the cutting operation.

29. A machine of the. class described, comprising wire coiling means, and means for cutting turns off the coiled wire, said cutting 10 means comprising relatively moving cutting elements, and wire gripping means whereby the wire at one side of the line of severance may be gripped during the cutting operation, a portion of one of the cutting elements being adapted to bear against a considerable'len of the coiled wire at the instant of cutting.

'30. A machine for making piston rings from hard steel Wire which comprises means for advancing a length of wire, means for confining the advancing wire so as to constrain it to assume an arcuate curvature, means for moving said confining means during the formation of a single'turn of the wire so as to vary the radius of curvature of the wire thereby to produce a turn of subtantially elliptical shape and means for severing the wire at such a point as to produce 7 a gap ad'acent tolone end of the minor axis of the elliptical turn. v Signed byme at Boston, Massachusetts,

this 24th day of Ma 1927.

' LE IS C. 

